The present disclosure relates generally to electronic displays and, more particularly, to liquid crystal displays (LCDs) that may be turned off in a manner that reduces or eliminates visual artifacts.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Electronic displays, such as liquid crystal displays (LCDs), are commonly used in electronic devices such as televisions, computers, and phones. LCDs portray images by modulating an amount of light that passes through a liquid crystal layer within pixels of varying color. For example, by varying a voltage difference between a pixel electrode and a common electrode in a pixel, an electric field may result. The electric field may cause the liquid crystal layer to vary its alignment, which may ultimately result in more or less light being emitted through the pixel where it may be seen. By changing the voltage difference (often referred to as a data signal) supplied to each pixel, images may be produced on the LCD.
To store data representing a particular amount of light that is to be passed through pixels, gates of thin-film transistors (TFTs) in the pixels may be activated while the data signal is supplied to the pixels. Conventionally, when an LCD is turned off, the pixel electrodes of all pixels of the LCD may be supplied a minimal voltage. When the TFT gates are deactivated, a kickback voltage may alter the voltage stored in the pixels. The resulting voltage may be different from the supplied minimal voltage and may cause an electric field that remains in place after the LCD is turned off. This electric field may continue to impact the liquid crystal layer of the pixels of the LCD while the LCD is off. It is believed that this electric field caused by the voltage on the pixel electrodes may result in image artifacts, such as flickering or horizontal/vertical lines, that could appear after the display is turned on again.
Moreover, a liquid crystal cell may contain a liquid crystal mixture (e.g., FLC mixture SCE13 in a ferroelectric liquid crystal display) that contains liquid crystals as well as ions. The ions may be classified as “fast-moving” ions and “slow-moving” ions. The fast-moving ions move quickly within the liquid crystal layer upon application of a voltage across the liquid crystal layer. Similarly, the slow-moving ions move slowly when a voltage is applied across the liquid crystal layer. The fast-moving ions typically can move around within the liquid crystal freely, but the slow-moving ions tend to move significant distance when a charge remains across the liquid crystal layer over a period of time. For example, a voltage difference may remain across the liquid crystal layer when the LCD is turned off and a kickback voltage creates a voltage difference between a pixel electrode and common electrode across the liquid crystal layer. After some period of time, the slow-moving ions may move to form one or more sheets of ions that may create electric fields that result in a voltage bias that interferes with the intended behavior of the liquid crystal layer. Although it may be desirable to not include slow-moving ions, it may be impossible or impractical to remove all slow-moving ions from the liquid crystal mixture.